The deployment behavior of a gas cushion in a motor vehicle is usually designed to cover a situation in which the vehicle driver or a passenger is held by the safety belt with their back against the backrest of the seat, in other words is at a certain distance from the gas cushion deploying in a collision situation and usually falls forward into the already inflated gas cushion. It can, however, happen that the driver or a passenger is actually leaning forward at the time a collision situation occurs and, as a result, is hit by the deploying gas cushion. This so-called “Out-of-Position” (OoP) situation has already led to more serious injuries than would have resulted due to the actual collision alone without the gas cushion. Consequently, concepts have already been developed which detect the deployment behavior of the gas cushion and in the event of an obstacle being present in the deployment range of the gas cushion which leads to a reduced or even inhibited deployment prevent further inflation of the gas cushion.
A device in which the gas cushion is provided with interrogation units which are implemented as threads or tapes and comprise a scannable coding is disclose in European Application No. EP 0 812 741 A1. When the gas cushion is deployed, the threads or tapes are drawn along at the velocity of the front part of the gas cushion and stretch to a corresponding length in the interior of the gas cushion. An evaluation device scans the coding either mechanically or also capacitatively, inductively, optically or the like. In this way, it can determine whether there is an obstacle in the deployment range of the gas cushion. If such an obstacle is detected, the gas supply is reduced or stopped altogether in order to avoid an injury to a person forming the obstacle.
However, problems with the known device are a complicated and therefore expensive manufacturing process and unsatisfactory reproducibility of the measurement result.